Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $114.53   10.760%   $126.8534   $126.85   $126.85   $126.90  
  Purchase #2 $214.30   8.558%   $232.6398   $232.64   $232.65   $232.60  
  Purchase #3 $192.65   8.702%   $209.4144   $209.41   $209.40   $209.40  
  Purchase #4 $118.30   10.286%   $130.4683   $130.47   $130.45   $130.50  
  Purchase #5 $54.78   11.313%   $60.9773   $60.98   $61.00   $61.00  
  Purchase #6 $113.50   11.669%   $126.7443   $126.74   $126.75   $126.70  
  Purchase #7 $116.38   10.731%   $128.8687   $128.87   $128.85   $128.90  
  7 purchase totals = $924.44       $1,015.9662   $1,015.96   $1,015.95   $1,016.00